Research Projects

Ammonia (NH3) is gaining significant attention as a carbon-free fuel and hydrogen carrier, which is crucial for decarbonizing sectors such as power generation, maritime transport, and industrial processes. While it offers easy storage and high hydrogen density, pure NH3 presents challenges due to its low reactivity, high ignition temperature, narrow flammability limits, and low laminar burning velocity. A major concern is the high NOx emission, primarily from fuel-bound nitrogen, unlike hydrocarbon fuels, where thermal NO dominates. Rich-burn, Quick-quench, Lean-burn (RQL) combustion is a promising strategy to mitigate NOx emissions by promoting N2 formation in a fuel-rich primary zone, followed by rapid quenching and a lean-burn stage. The in-situ generation of hydrogen in the rich stage significantly enhances ammonia's poor combustion characteristics, resulting in improved flame stability. However, challenges remain in optimizing residence times, refining kinetic mechanisms, and controlling N2O and unburnt ammonia slip. The core hypothesis is that RQL combustion can effectively reduce NOx emissions from NH3/H2 mixtures by strategically converting fuel-bound nitrogen to N2 in a rich-burn stage and preventing further NOx formation through rapid quenching and subsequent lean combustion. The project also implicitly tests the hypothesis that blending ammonia with hydrogen will enhance flame stability and expand flammability limits, and that specific operating parameters (pressure, preheat temperature, equivalence ratios, swirl number, and blending ratios) can be optimized for ultra-low NOx emissions while maintaining high efficiency and minimizing N2O and NH3 slip. Numerical simulations using a Chemical Reactor Network (CRN) model and Large Eddy Simulations (LES) with a transported FDF approach will be used to understand chemical kinetics and reaction pathways, aiding in combustor design and validation against experimental data. The project focuses on several key work packages designed to advance RQL combustion research. First, a laboratory-scale high-pressure RQL combustor will be developed, utilizing SS-316 steel and designed with optical access and a staged combustion chamber. Experimental investigations will generate a stability map and analyze NOx emissions for an RQL combustor operating at a fixed thermal power of 30 kW. Alongside high-speed PIV and OH-PLIF imaging, transient flame-turbulence interaction will be studied, while NO PLIF will be used to visualize NO production within the flame. Experimental investigations will be complemented by numerical simulations using a Large Eddy Simulation (LES) approach based on the filtered density function (FDF) with detailed chemical kinetics available in the literature. This project aligns with India's National Hydrogen Mission and its commitment to decarbonization and energy transition, addressing the need for carbon-free energy systems. India's significant ammonia production positions it to utilize ammonia as a clean hydrogen carrier and renewable fuel. The work will contribute to the development of advanced optical diagnostic techniques (NO-PLIF, PIV, OH-PLIF/NO PLIF, OH* chemiluminescence) for understanding the fundamental concepts and challenges in ammonia gas turbine combustion environments. The knowledge and techniques developed will apply to other combustion systems, fostering collaborations both domestically and internationally. This will aid in the development of indigenous fuel-flexible gas turbine combustion systems in India, fostering economic growth and job creation in the clean energy sector.